1. Field of the Invention
The present invention relates to workstations in general and, in particular, to multi-media workstations in which full motion video images and computer generated information (graphic and non-graphic) are shown on displays.
2. Prior Art
The proliferation of multi-media workstations creates the need for new techniques and/or devices to process multi-media information. Generally, the multi-media workstation is capable of processing electrical signals representative of voice, data, and video information. As a general proposition, the different types of information (i.e., data, voice, or video) are propagated on a common transmission medium.
A conventional workstation is comprised of a controller, which is usually a personal computer (PC), and one or more Input/Output (I/O) devices. The I/O devices may include printers, displays, etc,. The display unit is an important I/O device. It gives a user a visual image of information inputted into the system and results based upon queries from the user. A conventional device, commonly known as a video adapter, couples the display device to the bus of the PC. An operating system, such as OS/2.sup.R, is executed on the PC and provides the necessary facilities (e.g., interfaces, protocols, format, etc.) for providing information on the display via the video adapter. The OS/2.sup.R product includes multitasking features which allow it to partition the display screen into separate areas or windows in which selected information can be inserted and displayed to the user.
It is desirable for multi-media applications to display full motion video simultaneously with conventional computer graphic information in a windowing environment. Many primary sources of full motion video are in a format known as National Television Standards Committee (NTSC). An NTSC video image is composed of successive frames. Each frame consists of an interlaced odd and even field. Each field has 262.5 scan lines, approximately 240 of which contain video information. Therefore, each frame has 480 interlaced lines of video information.
The mixing of Real-Time Video information with computer originated graphics information on a window display screen presents several significant challenges in the development of a robust and reliable multi-media workstation.
Among the challenges is the protection of graphic windows with graphic information and/or icons (called protected information) from being obliterated (overwritten) by video or other realtime information in the Real-Time Video Window (RTVW) The protected information is usually positioned in the RTVW. The protected information could be considered as being static (i.e., changes less often), whereas the video information is dynamic (changes more often). In fact, every picture element (Pixel) in the RTVW is overwritten up to sixty times per second, whereas the graphic information is written less frequently. Unless devices are provided to protect the static data, it would be destroyed. It is this problem the present invention addresses.